Variable convergence hitch link structure



R. W. WILSON Sept. 18, 1956 VARIABLE CONVERGENCE HITCH LINK STRUCTURE 2Shee ts-Sheet 1 Original Filed Nov. 1, 1951 IN V EN TOR.

R4 wk 0; w. w/4 soA/ BY Sept. 18, 1956 R. w. WILSON VARIABLE CONVERGENCEHITCH LINK STRUCTURE 2 Sheets-Sheet 2 Original Filed Nov. 1, 1951 IN VEN TOR.

ATTOIP/VIY United States Patent ice.

VARIABLE CONVERGENCE HITCH LINK STRUCTURE Raymond W. Wilson, 'Ferndale,Mich., assignor to Ford Motor Company, Dearborn, Mich., a corporation ofDelaware Substituted for abandoned application Serial No. 254,368,November 1, 1951. This application April 12, 1954, Serial No. 422,368

'4 Claims. (Cl. 97-4166) The present invention relates to variableconvergence tractor hitch links, and more specifically to variableconvergence links wherein relative lateral tractor-implement movement istranslated into implement-steering movement by the differential pivotedmovement of a pair of trailing hitch link elements for steering animplement on the linkage about an efiective steering point determined bythe angular relationship of the link elements in a lateral plane.

This application is a substitute for my application Serial No. 254,368,filed November 1, 1951, now abandoned.

In my earlier filed U. S. Patent 2,653,823, dated September 29, 1953,and in U. S. Patent 2,653,824, also dated September 29, 1953, by RalphC. Frevik, both of said patents being assigned to the assignee of thepresent invention, there are disclosed tractor-implement connectionsincluding pairs of links each consisting of a pair of trailing linkelements connected at their forward ends to laterally spaced portions ofthe tractor rear axle and connected at their rear ends to an implementcross shaft through laterally extending crank arms. The presentinvention provides an improved hitch wherein a vertically extendingcrank arm is utilized for implement steering. Among the advantagesgained by the present structure are the improvement of lateral clearanceto accommodate greater relative lateral tractor-implement movement, theelimination of universal bearings formerly necessary for thetractor-linkage connection, the simplification of the entire structureto insure lower cost and greater ease of manufacture, and the moreaccurate determination of the effective steering point by the angularrelationship of the link elements.

structurally, the present invention includes a pair of laterally spacedhitch links each comprising a pair of trailing link elements pivotallyattached to an attachment bracket, the link elements being secured tothe bracket for lateral movement only and the bracket being attached tothe tractor rear axle for vertical pivoting movement only. One of thelink elements is adjustable laterally of the bracket to vary the angularrelationship of the elements, and the elements of each link areconnected at their rear ends to the implement through a verticallyextending crank arm. At one adjusted position of ,the movable linkelement, the elements of each link are more or less vertically alignedand move laterally in substantially identical arcuate paths, while inanother adjusted position, the elements are forwardly divergent and movein substantially differing arcuate' paths. In the first named position,the substantially identical paths oftravel cause the crank arm to behaveas though it were moving about a steering point located at the normaltheoretical point of convergence of the pairs of links, i. e., in thevicinity of the tractor front axle. 'On the other hand,

the movement of the elements in widely differing paths causes theeffective lengths of the elements to vary more or less drastically andthe vertical crank arm is subjected to the resulting differentialarcuate movement of the ele- 2,763,194 Patented Sept. 18, 1956 ments. Asa result, the implement is steered as though it were pivoted for lateralmovement about a steering point located in the vicinity of the tractorrear axle.

It is, therefore, an important object of the present invention toprovide an improved tractor hitch link arrangement wherein relativelateral tractor-implement movement is translated into vertical movementat the implement-attaching portions of the linkage for steering theimplement about an effective steering point.

Another object is the provision of a variable tractorimplement linkagehaving laterally spaced link elements each connected to a verticalsteering crank arm and effective to steer an implement through the armsabout a steering point located by the angular relationship of the linkelements.

It is a further important object to provide a tractorimplement linkagewherein the linkage is pivotal about separate horizontal and verticalaxes to support an implement for lateral steering movement about a pointlocated on the tractor and determined by the angular relationshipbetween certain of the link elements.

Still anotherobject of the present invention is the provision of alinkage including spaced pairs of trailing link elements connected atcorresponding ends to a vertical crank arm and adjustable laterally todifferent relative angular positions in which the paths of individuallink movement in a lateral plane vary more or less drastically to causea corresponding variance in the longitudinal position of the effectiveimplement steering point.

The specific nature of this invention, as Well as other objects andadvantages thereof, will become apparent to those skilled in the artfrom the following detailed description, taken in conjunction with theattached sheets of drawings on which, by Way of preferred example only,is illustrated one embodiment of this invention.

On the drawings:

Figure l is a side elevational view of a tractor having one wheelremoved for clarity and connected to an implement through hitch links ofthe present invention;

Figure 2 is a plan view of the tractor and hitch links of Figure 1illustrating the linkage in one adjusted position;

Figure 3 is a plan view similar to Figure 2 illustrating the linkage ina different adjusted position;

Figure 4 is a greatly enlarged plan view of the linkage aloneillustrating the operation of the linkage when in the adjusted positionof Figure 3;

Figure 5 is a view similar to Figure 4 illustrating operation of thelinkage when in the adjusted condition of Figure 2;

Figure 6 is an elevational View taken along the plane 6--6 of Figure 4;

Figure 7 is a view taken along the plane 7-7 of Figure 5; and

Figure 8 is a fragmentary enlarged side elevational view of the forwardportion of the linkage illustrating its attachment to the tractor.

As shown on the drawings:

In Figure 1, reference numeral 10 refers generally to a tractor, such asa Ford tractor, having a rear axle housing 11 and power-liftable rockarms 12 connected to the conventional tractor hydraulic system, as iswellknown in the art. The rear axle housing is also surmounted by acontrol bracket 13 pivoted, as at 14, to the rear axle housing andcarrying a trailing top link 15 pivoted thereto for reaction against thehydraulic system control spring 16. The top link is pivoted, .as at 17,to the upper end of an A-frarne 18 of an implement 19 such as a plow.The implement cross shaft 20 is connected to the tractor by means oftrailing laterally spaced draft link structures 21 of the presentinvention.

More specifically, the draft link structures 21 include a from attachingbracket 22 (Figures '4, and 8), the bracket comprising an axiallyapertured portion 23 receiving therethrough a mounting pin 24 supportingthe bracket for movement about a horizontal axis defined by the pin. Thethreaded inner end of the mounting pin is received by the rear axlehousing 11 and the central bracket portion 23 is provided at its outerextremity with a forwardly extending projection 25 having a mountingaperture 26. The inner end of the portion 23 carries a rearwardlyextending clevis defined by upper and lower plates 27 welded orotherwise secured to the center portion 23. The plates 27 are providedwith vertically registering apertures 28 adapted to receive therethrougha pivot pin 29 for a purpose to be hereinafter more fully described. Theupper plate 27 is extended forwardly to provide a second projection 34)identical with the projection 25 and also having an aperture 33thercthrough.

First link elements 32 are each provided with a forward embossment 33apertured at 34 for registry with the apertures 28. The pivot pin 29 isadapted to extend through the registering apertures 28 and 34 to supportthe element 32 for lateral swinging movement about a substantiallyvertical axis. Each of the elements 32 is laterally offset intermediateits length for reasons to become hereinafter apparent, and theintermediate portion is apertured to receive a locking pin 35 extendingthrough a terminal clevis 36 carried by lift arms 37 pivotallyconnected, as by joint 38, to the rock arms 12. Thus, the link elements32 may be power-lifted through actuation of the rock arms 12.

The extreme trailing rear portion of the link element 32 is transverselyapertured to receive therethrough a pivot pin 39 joining the element 32to a normally substantially vertically extending crank arm 40. The crankarm 40 comprises a pair of side plates 41 receiving the terminal end ofthe element 32 therebetween and apertured to receive the pivot pin 39.The lower extreme ends of the plates 41 carry therebetween a segmentalspherical attachment bearing 42 fixedly secured thereto. As best seen inFigures 1, 2 and 3, the segmental spherical attachment bearings 42 areadapted to be secured to laterally extending mounting pins 43 carried bythe implement cross shaft 20.

A second link element 44 of substantially greater length than theelement 32 is adapted to be attached to either of the bracketprojections 25 and 30 by means of a vertical pivot pin 45 extendingthrough an aperture at the forward end of the arm 44 and selectivelyenterable in either of the apertures 31 and 26 of the projections 30 and25, respectively. A mounting collar 46 is adapted to be interposedbetween the forward portion of the arm 44 and the bracket projection towhich it is secured to insure vertical clearance between the elements 32and 44.

The rear end of the element 44 is of reduced thickness, as at 47, forinsertion between the plates 41 of the crank arm 40, and a pivot pin 48is provided to pivotally join the element portion 47 to the crank arm40. It will be appreciated that the pivot pin 45 may be utilized tosecure the forward portion of the arm 44 in either of the positionsillustrated in Figures 4 and 5. When the pin 45 is inserted in theaperture 31, the arm 44 occupies the position of Figure 3, the resultingpivoting action of the arms 32 and 44 as a whole is as illustrated inFigure 4. The forward pivoting axes of the arms are substantiallylongitudinally aligned, and the elements themselves are substantiallyvertically aligned. Due to the difference in length of the elements, therear portion of the element 32 will travel in an arc 13a, the rear endof the element 44 will follow an arc 44a, and the center of theattachment bearing will follow an are 420. It will be noted that thesearcs substantially coincide and the location of the center about whichthe arcs are generated, i. e., the effective steering point of theimplement, will approximate the point 50 of Figure 3 which is in thevicinity of the tractor front axle. steering will follow tractorsteering.

When the element 44 is shifted laterally so that the pivot pin 45 isinserted in the aperture 26 of the projection 25, as illustrated inFigure 5, it will be seen that the forward portions of the elements 32and 44 are substantially laterally spaced, and the elements 32 and 44are forwardly divergent. Upon relative lateral tractor-implementmovement, the arm 32 will again follow the arc 32a, while the rear endof the element 44 will follow the arc 44b and the center of theattachment bearing 42 will follow the arc 42b. The effect of suchlateral movement is illustrated in Figure 7, wherein it will be seenthat the crank arm 40 is inclined with respect to a vertical plane 51,and the are 42b followed by the attachment bearing 42 is centered at apoint 52 located in the vicinity of the tractor rear axle housing. InFigure 7, the adjusted vertical position of the left crank arm 40 isshown in full lines and the outline of the right crank arm is shown indotted lines to illustrate the implement steering action as the crankarms are moved. As has been explained in the above identified earlierapplications of myself and Ralph C. Frevik, respectively, steering aboutsuch a point 52 is desirable where implements such as moldboard plowsand disc plows which generate substantial unbalanced side draft forcesare utilized.

Thus, it will be seen that the present invention provides an improvedtractor-implement linkage wherein vertically extending crank armsadapted for connection to an implement are forced to follow a lateralare having its center located by the angular relationship of a pair ofhitch link elements connected to the crank arm. In other words, thearcuate paths of movement of a pair of hitch elements determine the pathof movement of an implement carried by a vertical crank arm joining theelements, and the differential pivoting movement of the elements causessteering of the implement about a desired effective steering point.

It will be understood that the invention is not to be limited to theexact construction shown and described, but that various changes andmodifications may be made without departing from the spirit and scope ofthe invention, as defined in the appended claims.

What is claimed is:

1. A variable convergence linkage for attaching an implement to atractor comprising a pair of laterally spaced trailing hitch linkstructures on the tractor, each of said structures including anattaching bracket pivotally secured to the tractor for movement in avertical plane, a first link element attached to the bracket for lateralswinging movement, at second link element attachable to the bracket atone of a plurality of laterally spaced points, including a first pointat which said first and said second elements are substantiallyvertically aligned and a second point at which said first and saidsecond elements are forwardly divergent, and a vertical crank armjoining the free rear ends of said elements and attachable to animplement to steer the same laterally about an effective steering pointdetermined by the point of attachment of said second element.

2. In an implement-tractor linkage, a pair of laterally spaced forwardlyconvergent trailing draft link elements having their forward endsoperatively attached to a tractor for free lateral swinging movement,vertically extending crank arms on the free rear ends of said draft linkelements having attachment bearings at one end thereof, and additionallink arms attached at their rear ends to the other ends of said crankarms, means on the forward ends of said link arms and adapted forselective operative attachment to the tractor, the forward ends of saidlink arms being attachable in vertical alignment with the correspondingends of said draft link elements whereby said attachment bearings areeffectively steered about the theoretical point of convergence of saiddraft link elements, and said forward ends of said link arms also beingattachable in laterally spaced relation to the forward ends of saiddraft link elements whereby said link arms limit the lateral Thus,implement movement of said attachment bearings .to steer the same abouta point longitudinally displaced from said theoretical point ofconvergence.

3. In an implement-tractor linkage, a pair of laterally spacedindependent attachment brackets journaled for pivotal movement about ahorizontal axis on the tractor, a pair of vertically extending crankarms having attachment bearings respectively adapted for pivotalattachment to an implement, a pair of forwardly converging first linkelements joining said crank arms to said brackets and laterallyswingable relative to said brackets about vertical pivot axes tonormally cause swinging movement of said attachment bearings about thetheoretical convergence point of said first link elements, and secondlink elements each secured to one of said crank arms and selectivelyattachable to one of said brackets, respectively, at a pair of laterallyspaced points including (1) a first point at which said first and secondlink elements are vertically aligned at said bracket and swingingmovement of said attachment bearings occurs about said point oftheoretical convergence, and (2) a second point at which said secondlink elements are pivoted to the brackets in laterally spaced relationto said first elements to modify swinging movement of said attachmentbearings so that the implement is steered about an effective pointrearwardly of said point of theoretical convergence.

4. In an implement-tractor linkage, a pair of laterally spaced trailinghitch link structures, each including first and second link elements,said first elements being attachable at one end to said tractor andbeing forwardly convergent toward a theoretical attachment point, afreely swingable vertical crank arm at the other end of each of saidfirst elements for pivoted attachment to the implement, and said secondelements each being attachable at one end to the tractor at one of apair of predetermined laterally spaced points and attachable to saidcrank arm in vertically spaced relation to said first element, each ofsaid second elements at one of said attachment points being insubstantial vertical alignment with the corresponding first element sosaid implement is steered about said theoretical convergence point, andeach of said second elements at a second attachment point beingforwardly divergent with respect to said corresponding first element sothat the implement is steered about a point displaced from saidtheoretical convergence point.

References Cited in the file of this patent UNITED STATES PATENTS1,916,945 Ferguson July 4, 1933 2,653,825 Collins Sept. 29, 19532,673,508 Richey Mar. 30, 1954

